The sealing stamp was found during archeological research in 2014, as a secondary find, in an old sandpit, in an area where arable fields along the road from Bierzyn to the manor stretched in the 13^th–16th centuries. It has the shape of a shield 37 × 33 mm and a thickness of approx. 3 mm. It was made of lead. Framing legend: + SIGILLUM LUTOLD [I] H [AKE]. It comes from the mid or second half of the 14th century, as indicated by the typeface and coat of arms. The heraldic sign was presented in an interesting form of a stylized tree branch in a pole, different from the one used by the Silesian Hack family. Perhaps it belonged to Lutold, the knight known from several documents from the second half of the 14th century. The place of discovery suggests his journey through the Duchy of Ziębice: to Strzelin (in the city of the monastery there was a monastery popular among Silesian knights Poor Clares) or to an unrecognized private headquarters in Bierzyn. The authors present the medieval history of the Hack family and the seals they used. The article is accompanied by illustrations with, among others, stamp photos.